The present invention relates to a surface-indented covering member having irregularities on its surface forming the outer side of an instrument, an appliance, and parts, which are industrially manufactured, such as television, radio, tape recorder, compact disk player, optical disk player, video tape recorder, camera, video camera, cleaner, washing machine, refrigerator, toaster, juicer, mixer, electric iron, air conditioner, personal computer, word processor, floppy disk driver, hard disk driver, telephone, wireless appliance, interphone, speaker, laser beam printer, PPC, facsimile, battery, capacitor, magnetic tape cassette, motor, actuator, encoder, bicycle, motorbicycle, car, heating appliance, microwave oven, electric fan, clock, illuminating instrument, and toy. More particularly, the present invention relates to the surface-indented covering member which improves the value of a commodity by making the color tone of the surface thereof aesthetically pleasing.
The term surface-indented covering member refers to body, a case, a sheath, a housing, a box, or a panel. The surface-indented covering member is provided on the surface of instruments, appliances, and parts which are industrially manufactured in order to protect the function thereof, improve the safety thereof and give them a pleasing appearance.
In order to make a product aesthetically pleasing, manufacturers consider the following three elements in producing a surface-indented covering member so that the product has a pleasant texture such as soft or hard, rich, functional, aesthetically beautiful, and fresh: the entire outline configuration of the product; the three-dimensional configuration which is determined by the arrangement of a button, knob, lever, dial, or the like; and a color design determined by color, brightness, and gloss.
According to a technique used as a means for giving a favorable color to a product, natural materials such as wood, stone, and fur are cut, ground, or connected with each other to use them as surface-indented covering members without degrading the appearance thereof. But these natural materials are expensive and used for limited products, for example, high class products.
Generally, industrial products are coated with surface-indented covering members composed mainly of a metal plate such as of iron or aluminum; a plastic molding; or a plastic sheet. Depending on the product, glass, cloth, or paper may additionally be used. The following techniques are used to manufacture surface-indented covering members: The surface of iron, aluminum, and plastic molding is smoothed; rough irregularities are formed on the surface thereof (which is called an embossing process); a hairline process is used; particles such as pigment are dispersed in the material of the member; a resin which contains dye or pigment is applied to the surface of the main body; and metal powders are contained in the plastic molding so as to make customers feel as if the product were made of metal. Parts produced as above are combined with each other so as to adhere or engage a combined material to the main body, or such that it can be pressed onto the main body by hot-stamping or welding.
These techniques depend on a material or an additive such as a dye or pigment to function for selectively reflecting light of a specific wavelength from among light of various wavelengths, which has been incident on the surface of the surface-indented covering member. According to these techniques, light quantity and direction of light which has been incident on the surface of the surface-indented covering member and reflected thereby are determined by the degree of roughness of the product surface of the member.
However, in consideration of the spectral characteristic of absorption/reflection in the visible region, there are few materials which reflect a specific wavelength. Therefore, colors of the surface-indented covering member look dull. Particularly, blue and green are perceived to be dull.
As such, light quantity and direction of reflected light are not as favorable as intended because of an unfavorable degree of irregularity.
On the other hand, in compact disks and optical disks which have been developed recently, light waves which have been reflected by grooves formed on the surface thereof interfere with each other. Therefore, a specific wavelength is emphasized, which gives the product a different appearance.
Referring to FIG. 3 which is a partial sectional view showing the surface of a disk which provides an interference color, an aluminum film 3 is evaporated onto the upper surface of a transparent substrate 1 having projections 2 formed on the upper surface thereof. Light 4 which has been incident on the lower surface 5 of the transparent substrate 1 is reflected by the aluminum film 3. The disk gives a favorable impression on the eye. This phenomenon is generated because of the interference color. That is, each light having a wavelength equal to the optical path difference between light 6 reflected by the aluminum film 3 not corresponding to the projection 2 and light 6' reflected by the aluminum film 3 corresponding to the projection 2 interferes with each other.
Utilizing this principle, a surface-indented covering member comprising an ornamental transparent film which is to be stuck to a product is commercially available. With to the film, the direction of reflected light is controlled by a devised pattern configuration.
According to the above conventional art, optical path differences are slightly different from each other according to the incident and reflection angle of light. As a result, reflected interference colors form a rainbow. If the wavelengths of interference colors are out of the visible region, aluminum looks as it is. The conventional art has a limitation in giving a favorable color to the product.